Uncategorized 21 May 2005 03:44 pm
Manufacturing jewelry with a Fresnel lens
Josh and I checked out the University Street Fair today and came home with some neat stuff. By far the coolest booth in my opinion was the one belonging to Sundrop Jewelry. They make very pretty glass drop beads with scrap glass and a giant Fresnel lens. I am now the happy owner of a pair of their earrings in a lovely smoky color. (Thanks, Josh!)
There are some movies at the Sundrop site of making jewelry and burning things with the Fresnel lens. Wow, that thing is powerful. Imagine all the things you could do with one of those… I’m kind of kicking myself for not buying a giant Fresnel at auction from the UW a few years ago, but then again, for all I know that’s the very lens that heated the glass for my earrings.
on 21 May 2005 at 4:15 pm 1.Ted said …
You NEED a giant Fresnel lens! Just think of all the… um… gardening you could do with it!
on 21 May 2005 at 4:19 pm 2.Cam Sculpin said …
Fire gardening! Yes, that’d take care of the grass just fine.
on 21 May 2005 at 6:05 pm 3.cissa said …
Hmm. The jewelry looks really cool, but I’d be pretty concerned about the glass exploding at some point. When one combines glasses with unknown coefficients of expansion, that’s a risk- and even when things have similar coefficients of expansion, it’s a Good Idea to anneal the glasses after forming to prevent explosion from internal stresses. I don’t see how one can anneal with a big lens like that…
I don’t think earrings are all that dangerous, but it’s something to keep in mind for larger stuff.
on 21 May 2005 at 6:08 pm 4.mallard said …
Saaaaay … I’ve got a Fresnel lens in my unused opaque projector. I think I offered it to you guys once before, but you were in the midst of a big decluttering stage. Might you be interested now?
on 21 May 2005 at 7:30 pm 5.Cam Sculpin said …
Cissa: Got me. I know squat about glassworking. The glassworkers all still seem to have their eyes intact, though. Since they use scrap art glass for the multicolor drops, not bottle glass, they may have good information on those glasses’ coefficients of expansion. (And while they’re obviously proud of the multicolored glass work, from the looks of the stuff at the stand it isn’t most of what they do.)
I wouldn’t be too surprised if they had the occasional problem, though. I notice that they aren’t advertising for students.
Mallard: Saaaaaaaay. I remember that now. Ooh. I might be.
on 22 May 2005 at 3:54 pm 6.MaLora said …
have you ever met Aaron Ford? he is friends wtih Jake & me and i know he’s met Josh. anyway, those sundrop earrings are made by his friends! i bought some last year as well.
the lens is awesome isn’t it?
on 22 May 2005 at 5:47 pm 7.Cam Sculpin said …
Never have met him, as far as I know. Small world! Small town, anyway.
on 23 May 2005 at 10:59 am 8.Hig said …
Ah, the internet…
I remember you buying the smokey bottle glass… It’s one of our favorite colors because it’s so unusual.
Too bad the weather didn’t allow for a demo this weekend.
I suppose you weren’t looking for a lecture on glass compatability, but…
Coefficient of expansion vs. annealing/tempering glass:
These are essentially two different issues. You do need to know the coefficient of expansion if you mix glass colors. This is why we do not mix bottle glass at all. We just use the bottle glass to make monochrome drops. If you mix glass with different coefficients of expansion, it doesn’t matter whether you anneal it or not, it’s likely to break. The multicolored glass is mostly Bullseye glass (we collect scrap from stained glass artists, and also buy some glass for colors we can’t find in scrap.) Bullseye produces all its glass with the same coefficient of expansion.
However you’re right, we do not anneal our glass. In many cases this would be a problem. However, because the Sundrops are small, and because they have a very simple shape (all convex in the area where it’s thick enough to have problems) it’s actually an advantage to temper (not anneal) the glass.
Basically what happens is that as the glass cools quickly, the surface of the glass becomes hard before the core. This means that the core overcontracts relative to the surface, leaving the core in tension, and the surface in compression. The compression means that it’s very hard for a crack to start on the surface of the drop… Similar to a tempered windshield.
Overall the drops are not tempered enough to ever “explode”. Some break during the process of handling them (particularly putting on the wire wrap.) It’s possible to more highly tempre drops to get “Prince Rupert’s drops” which do explode, see for example:
http://www.cmog.org/index.asp?pageId=735
on 23 May 2005 at 10:01 pm 9.Cam Sculpin said …
I am always looking for a lecture on glass compatability.
Thanks! Good to hear from you!
on 22 Dec 2006 at 8:09 am 10.rjl20: Street Fair Favorites said …
[...] Josh (rjl20) wrote,@ 2005-05-24 22:37:00 Street Fair Favorites Some favorites from last weekend’s University District Street Fair:Verone Flood, photographer. She’s got some really nice compositions, and I like the triptych-like presentation style. There were a few designs at her stall that aren’t on her web site, and one of them I was thinking about buying. I guess I’ll have to email her and ask about it.Mud In Your Eye Pottery. They’ve got some beautiful glazes, and a very well designed mixing bowl. Also, a water crock that was too useful to pass up. I want to visit them next time I’m up in Bellingham.Sundrop Jewelry, glass jewelry made with a giant fresnel lens. Awesome. Cam posted about them, too.[ 5 Comments ] [...]
on 20 Apr 2009 at 11:38 am 11.martin nix said …
yea gang, can you email a photo of the frame and frenel lens you use, i got some people over at sustainable ballard who want to do an article on solar smelting. best martin
forward to rhonda@sustainableballard.org
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